Scroll machines can be used to compress, expand or pump fluids and include two scroll members each of which has a circular end plate and a spiral or involute wrap. The scroll members are maintained angularly and radially offset so that both wraps interfit to make either a plurality of line contacts or are spaced by minimum clearances between the wraps to thereby define at least one pair of fluid pockets or chambers. One scroll member is stationary and the other orbits due to an eccentric shaft and an antirotation coupling. The relative orbital motion of the two scroll members shifts the line contacts or minimum clearances along the curved surfaces of the wraps so that the trapped volumes in the fluid pockets change in volume. The trapped volumes can increase or decrease depending upon the direction of orbiting motion. Because several trapped volumes generally exist at the same time, several line contact or minimum clearance points also exist at the same time with each moving along the wraps with movement being towards the center or discharge port in the case of a compressor. Since the points of line contact or minimum clearance represent locations of potential wear and/or leakage, it is imperative that the scroll wraps be accurately machined and matched.
Since the fixed and orbiting scroll wraps are of the same configuration but are angularly and radially offset with respect to each other, the machined slots defining the wraps are of the same width or radial extent. However, inaccuracies in the machine process, tool wear, differential thermal expansion, etc. can negatively influence the uniformity of dimensions with resultant interference or leakage. Additionally, it may be desirable to coat the wrap(s) with a suitable surface coating which can change the dimensions of the wrap(s).